It is well understood that a boiler operates at high temperatures and components within the boiler must be able to withstand extreme conditions that exist therein.
One such component is a stainless steel boiler tube through which water and/or steam flows.
Hot combustion gases carrying abrasive particulates, such as fly ash, flow over the tubes. The particulates will abrade and erode the tubes. As a result, the tubes will have a short life without protective measures.
It is conventional to protect a boiler tube in the path of the gas stream with a stack of sacrificial “shields”. These shields are semi-circular, elongate, stainless steel members that are each secured to the tube by u-shaped clamps that extend around the back of the tube and are welded to the side edges of the shields. It is not uncommon for as many as three shields to be stacked and separately clamped on a boiler tube with the objective of protecting the tube for about a two year or longer period.
It is typical practice to shut down and open the boiler for inspection and maintenance about every 1 to 1½ years. Typically, one will find on the first shut-down that one or two of the shields will have been so eroded that they have fallen off or need to be replaced. This is then done and the boiler is placed back in service. On the second shut-down, all of the shields on the tube are usually removed and a new stack is applied.
During a boiler shut-down, this replacement of the shields can be the operation that determines the length of the shut-down. Removing and replacing the shields involves considerable welding and consumption of welding manpower.
As a consequence, there has long existed a need to develop a better sacrificial shield which has extended durability. It is the objective of this invention to address this need.